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    Subject[PATCH 4.14 20/48] rtnetlink: add rtnl_link_state check in rtnl_configure_link
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Roopa Prabhu <roopa@cumulusnetworks.com>

    [ Upstream commit 5025f7f7d506fba9b39e7fe8ca10f6f34cb9bc2d ]

    rtnl_configure_link sets dev->rtnl_link_state to
    RTNL_LINK_INITIALIZED and unconditionally calls
    __dev_notify_flags to notify user-space of dev flags.

    current call sequence for rtnl_configure_link
    rtnetlink_newlink
    rtnl_link_ops->newlink
    rtnl_configure_link (unconditionally notifies userspace of
    default and new dev flags)

    If a newlink handler wants to call rtnl_configure_link
    early, we will end up with duplicate notifications to
    user-space.

    This patch fixes rtnl_configure_link to check rtnl_link_state
    and call __dev_notify_flags with gchanges = 0 if already
    RTNL_LINK_INITIALIZED.

    Later in the series, this patch will help the following sequence
    where a driver implementing newlink can call rtnl_configure_link
    to initialize the link early.

    makes the following call sequence work:
    rtnetlink_newlink
    rtnl_link_ops->newlink (vxlan) -> rtnl_configure_link (initializes
    link and notifies
    user-space of default
    dev flags)
    rtnl_configure_link (updates dev flags if requested by user ifm
    and notifies user-space of new dev flags)

    Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/rtnetlink.c | 9 ++++++---
    1 file changed, 6 insertions(+), 3 deletions(-)

    --- a/net/core/rtnetlink.c
    +++ b/net/core/rtnetlink.c
    @@ -2402,9 +2402,12 @@ int rtnl_configure_link(struct net_devic
    return err;
    }

    - dev->rtnl_link_state = RTNL_LINK_INITIALIZED;
    -
    - __dev_notify_flags(dev, old_flags, ~0U);
    + if (dev->rtnl_link_state == RTNL_LINK_INITIALIZED) {
    + __dev_notify_flags(dev, old_flags, 0U);
    + } else {
    + dev->rtnl_link_state = RTNL_LINK_INITIALIZED;
    + __dev_notify_flags(dev, old_flags, ~0U);
    + }
    return 0;
    }
    EXPORT_SYMBOL(rtnl_configure_link);

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